Thread: Heartbeat between Primary and Standby replicas

Hello everyone,<br /><br />I am designing a heartbeat system between replicas to know when a replica goes down so that
necessarymeasures can be taken. As I see, there are two ways of doing it:<br /><br />1) Creating a separate heartbeat
processon replicas.<br /> 2) Creating a heartbeat message, and sending it over the connection that is already
establishedbetween walsender and walreceiver.<br /><br />With 2, sending heartbeat from walsender to walreceiver seems
trivial.Sending a heartbeat from walreceiver to walsender seems tricky. Going through the code, it seems that the
walreceiveris always in the PGASYNC_COPY_OUT mode (except in the beginning when handshaking is done).<br /><br />Can
yourecommend the right way of doing this?<br /><br />Thank you.<br /><br />Regards<br /><br
/>---------------------------<br/>Postgres version = 9.0 beta-4<br /> 

On Fri, Sep 17, 2010 at 6:49 AM, fazool mein <fazoolmein@gmail.com> wrote:
> I am designing a heartbeat system between replicas to know when a replica
> goes down so that necessary measures can be taken. As I see, there are two
> ways of doing it:
>
> 1) Creating a separate heartbeat process on replicas.
> 2) Creating a heartbeat message, and sending it over the connection that is
> already established between walsender and walreceiver.
>
> With 2, sending heartbeat from walsender to walreceiver seems trivial.
> Sending a heartbeat from walreceiver to walsender seems tricky. Going
> through the code, it seems that the walreceiver is always in the
> PGASYNC_COPY_OUT mode (except in the beginning when handshaking is done).
>
> Can you recommend the right way of doing this?

The existing keepalive feature doesn't help?

Regards,

-- 
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center

Apologies. I'm new to Postgres and I didn't see that feature. It satisfies what I want to do.<br /><br />Thanks.<br
/><br/><div class="gmail_quote">On Thu, Sep 16, 2010 at 7:34 PM, Fujii Masao <span dir="ltr"><<a
href="mailto:masao.fujii@gmail.com">masao.fujii@gmail.com</a>></span>wrote:<br /><blockquote class="gmail_quote"
style="margin:0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div class="im">On Fri,
Sep17, 2010 at 6:49 AM, fazool mein <<a href="mailto:fazoolmein@gmail.com">fazoolmein@gmail.com</a>> wrote:<br />
>I am designing a heartbeat system between replicas to know when a replica<br /> > goes down so that necessary
measurescan be taken. As I see, there are two<br /> > ways of doing it:<br /> ><br /> > 1) Creating a separate
heartbeatprocess on replicas.<br /> > 2) Creating a heartbeat message, and sending it over the connection that is<br
/>> already established between walsender and walreceiver.<br /> ><br /> > With 2, sending heartbeat from
walsenderto walreceiver seems trivial.<br /> > Sending a heartbeat from walreceiver to walsender seems tricky.
Going<br/> > through the code, it seems that the walreceiver is always in the<br /> > PGASYNC_COPY_OUT mode
(exceptin the beginning when handshaking is done).<br /> ><br /> > Can you recommend the right way of doing
this?<br/><br /></div>The existing keepalive feature doesn't help?<br /><br /> Regards,<br /><font color="#888888"><br
/>--<br /> Fujii Masao<br /> NIPPON TELEGRAPH AND TELEPHONE CORPORATION<br /> NTT Open Source Software Center<br
/></font></blockquote></div><br/> 

On Mon, Sep 27, 2010 at 7:46 AM, fazool mein <fazoolmein@gmail.com> wrote:
> I checked the code for the keepalive feature. It seems that the socket
> options are only set on the primary's socket connection. The tcp connection
> created on the secondary for walreceiver does not use the keepalive
> parameters from the configuration.

You can use libpq keepalive parameters for walreceiver.

keepalives_idle
keepalives_interval
keepalives_count
http://developer.postgresql.org/pgdocs/postgres/libpq-connect.html

Those can be set in primary_connection in recovery.conf.

Regards,

-- 
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center